Monomers such as vinyl chloride monomer can be removed by heat and vacuum in most cases but this has several disadvantages: time, cost, energy input, possible thermal degradation of the polymer, difficulty in getting down to very low concentrations of the residual monomers such as vinyl chloride monomer, and extreme difficulty is experienced in getting vinyl chloride monomer out of "glassy" polyvinyl chloride. This is true regardless of how the polymer is produced, viz bulk, emulsion or solution polymerization.